Parts made by additive manufacturing are often structural in nature, rather than having functional properties conveyed by a polymer or other component. Printed parts having piezoelectric properties may be formed using a composite filament comprising a plurality of piezoelectric particles dispersed in a thermoplastic polymer. The composite filaments may be formed through melt blending and extrusion. The composite filament is compatible with fused filament fabrication and has a length and diameter compatible with fused filament fabrication, and the piezoelectric particles are substantially non-agglomerated and dispersed along the length of the composite filament. The piezoelectric particles may remain substantially non-agglomerated when dispersed in the thermoplastic polymer through melt blending. Additive manufacturing processes may comprise heating such a composite filament at or above a melting point or softening temperature thereof to form a softened composite material, and depositing the softened composite material layer by layer to form a printed part.